Screen-Printed Sensors Allow Earbuds to Record Brain Activity and Exercise Levels

University of California San Diego, La Jolla, CA

The screen-printed, flexible sensors are attached to the earbuds on a flexible, stamp-like surface. (Image: UCSD)

A pair of earbuds can be turned into a tool to record the electrical activity of the brain as well as levels of lactate in the body with the addition of two flexible sensors screen-printed onto a stamp-like flexible surface.

The sensors, developed by a team at the University of California San Diego, are a lot less cumbersome than state-of-the-art devices currently used to sense the brain’s electrical activity and the body’s sweat secretions.

“Being able to measure the dynamics of both brain cognitive activity and body metabolic state in one in-ear integrated device that doesn’t intrude on the comfort and mobility of the user opens up tremendous opportunities for advancing health and wellness of people of all ages, anytime and anywhere,” said Professor Gert Cauwenberghs.

The screen-printed, flexible sensors are attached to the earbuds on a flexible, stamp-like surface. The earbuds are secured with a silicon hook in order to be more stable in the ear.

“Earbuds have been around for decades, and in many ways were one of the first wearable devices on the market,” said Professor Patrick Mercier. “This research takes important first steps to show that impactful data can be measured from the human body simply by augmenting the capabilities of earbuds that people already use on a daily basis. Since there are no major frictions to using this technology, we anticipate eventual wide scale adoption.”

The first step in building the in-ear sensors was confirming that EEG and lactate data could be gathered in the ear. Researchers had to design smaller, more compact instruments to gather electrophysiological signals, such as EEG data, that would fit on an earbud. They also had to find a suitable material to collect sweat and sense lactate.

After preliminary experiments on human subjects, researchers determined that the best location to collect and record lactate data was the tragus, where sweat accumulates at the entrance of the ear. The team also knew from previous experience that to collect EEG data, high-performance physiological electrodes pointed toward the temporal lobe were required.

To make sure that the electrophysiological sensors had firm contact with the ear, researchers designed 3D, spring-loaded sensors that hold contact but can adjust as earbuds move. On the other hand, to improve sweat collection, researchers covered the electrochemical sensors with a see-through hydrogel film.

“This new and powerful in-ear multimodal wearable bioelectronic platform offers a rich source of real-time information on the health of the users, by recording simultaneously and dynamically physical and biochemical information,” said Professor Joseph Wang.

One of the devices’ limitations is that to gather enough lactate to meaningfully analyze data, subjects need to perform exercise or other physical activity that get people to sweat. In future work, researchers will aim to do away with this requirement.

The team is also working on processing the data on the device itself. Ultimately, the goal is to transmit the processed data wirelessly to a computer or a smartphone. In-ear sensors could also gather additional data, such as oxygen saturation levels and glucose levels.

Throughout the study, researchers conducted extensive experiments to validate the efficacy of the sensors.

“The ear canal has been relatively underexplored within the wearable technology community,” said Sheng Xu. “This work demonstrates the potential of continuous sensing to capture valuable physical and chemical signals from the ear canal thereby paving the way for numerous exciting opportunities in the field of wearables.”

For more information, contact Ioana Patringenaru at This email address is being protected from spambots. You need JavaScript enabled to view it..